Patent Document 1 below discloses a vehicle seat provided with a side airbag device that inflates and deploys a side airbag between door trim of a side door and the side of a seated occupant in the event of a side-on collision. In this related technology, a bracket is provided that covers a portion of the side airbag from the vehicle rear side and that is open towards the front side. Configuration is made with a structure in which the bracket is fixed to a seatback side frame at a seat width direction outer side, and a seat back board is fixed to the seatback side frame through the bracket. In side view of the seat, a front end portion of an airbag case is positioned further towards the vehicle front side than the seat back board and a front end portion of the bracket. In this configuration, the seat back board is fixed to the seatback side frame through the bracket, preventing the seatback board from impeding deployment of the side airbag. The bracket also functions to guide deployment of the side airbag towards the vehicle front side. Deployment characteristics of the side airbag are thereby improved, enabling swift deployment of the side airbag towards the vehicle front side.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2010-184668    Patent Document 2: Japanese Patent No. 3345279    Patent Document 3: JP-A No. H09-309400    Patent Document 4: JP-A No. H08-324372    Patent Document 5: JP-A No. 2010-241192    Patent Document 6: JP-A No. 2011-068197